Altermagnets versus Antiferromagnets

TL;DR

This paper introduces altermagnets, a new class of metals with momentum-dependent spin splitting, and develops a phenomenological model to compare their electronic spectra with antiferromagnets, revealing unique Berry curvature properties.

Contribution

It presents a phenomenological approach to describe altermagnets and compares their spectra to antiferromagnets, highlighting the conditions for nonzero Berry curvature.

Findings

Altermagnets exhibit momentum-dependent spin splitting.

Only weak ferromagnetic antiferromagnets have nonzero Berry curvature.

The spectrum of altermagnets can be mapped to that of antiferromagnets with similar symmetry.

Abstract

Altermagnets are metals with a momentum-dependent spin splitting of electron bands due to a specific crystal structure that is invariant under time reversal only in combination with rotations and reflections, or lacks time reversal altogether. The developed phenomenological approach allows one to obtain a spectrum of electron bands in an altermagnet corresponding to an antiferromagnet with the same symmetry. There are considered collinear antiferromagnets, weak ferromagnetic antiferromagnets, and ferrimagnetic structures. It is shown that only a weak ferromagnetic antiferromagnet has a nonzero Berry curvature.